feat: add heap sort

Author: codejsha

README.md

@@ -1188,7 +1188,7 @@ list.sort(Comparator.comparingInt(String::length));
 | **Worst**   |     $O(n + k)$      | when the input elements have a large range of values    |
 | **Average** |     $O(n + k)$      | when the elements are distributed randomly in the array |
 
-- Heap sort, CLRS#6: [java](/java-algorithm/src/main/java/com/example/algorithm/sort/HeapSort.java) | Heap sort is a comparison-based sorting algorithm that uses a binary heap data structure to sort an array. It is used for the implementation of priority queue.<br>($\textit{n}$ is the number of elements)
+- Heap sort, CLRS#6: [golang](go-algorithm/pkg/sort/heap_sort.go), [java](/java-algorithm/src/main/java/com/example/algorithm/sort/HeapSort.java) | Heap sort is a comparison-based sorting algorithm that uses a binary heap data structure to sort an array. It is used for the implementation of priority queue.<br>($\textit{n}$ is the number of elements)
 
 | **Case**    | **Time complexity** | **Remarks** |
 | ----------- | :-----------------: | ----------- |

go-algorithm/pkg/sort/heap_sort.go

@@ -0,0 +1,42 @@
+package sort
+
+import (
+	"golang.org/x/exp/constraints"
+)
+
+func heapSort[T constraints.Integer](arr []T) {
+	n := len(arr)
+	_buildMaxHeap(arr)
+	for i := n - 1; i > 0; i-- {
+		arr[0], arr[i] = arr[i], arr[0]
+		_maxHeapify(arr, 0, i)
+	}
+}
+
+func _buildMaxHeap[T constraints.Integer](arr []T) {
+	n := len(arr)
+	for i := n/2 - 1; i >= 0; i-- {
+		_maxHeapify(arr, i, n)
+	}
+}
+
+func _maxHeapify[T constraints.Integer](arr []T, i, n int) {
+	largest := i
+	for {
+		left := 2*i + 1
+		right := 2*i + 2
+
+		if left < n && arr[largest] < arr[left] {
+			largest = left
+		}
+		if right < n && arr[largest] < arr[right] {
+			largest = right
+		}
+		if largest == i {
+			break
+		}
+
+		arr[i], arr[largest] = arr[largest], arr[i]
+		i = largest
+	}
+}

go-algorithm/pkg/sort/heap_sort_test.go

@@ -0,0 +1,40 @@
+package sort
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"golang.org/x/exp/constraints"
+)
+
+func Test_heapSort(t *testing.T) {
+	type args[T constraints.Integer] struct {
+		arr []T
+	}
+	type testCase[T constraints.Integer] struct {
+		name string
+		args args[T]
+		want []T
+	}
+	tests := []testCase[int]{
+		{
+			name: "Integer Case",
+			args: args[int]{
+				arr: []int{31, 64, 49, 85, 71, 26, 6, 19},
+			},
+			want: []int{6, 19, 26, 31, 49, 64, 71, 85},
+		},
+		{
+			name: "Empty array input",
+			args: args[int]{},
+			want: nil,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			heapSort(tt.args.arr)
+
+			assert.Equalf(t, tt.want, tt.args.arr, "heapSort() got = %v, want %v", tt.args.arr, tt.want)
+		})
+	}
+}